Mitsubishi And The University Of Tokyo Quantify Factors For Reducing SiC Power Resistance

Wednesday 6th December 2017

Mitsubishi Electric Corporation and theUniversity of Tokyo have announced that they believe they are the first toquantify the impacts of three electron-scattering mechanisms for determiningthe resistance of silicon carbide (SiC) power semiconductor devices in power semiconductormodules. They have found that resistance under the SiC interface can be reducedby two-thirds by suppressing electron scattering by the charges, a discoverythat is expected to help reduce energy consumption in power equipment bylowering the resistance of SiC power semiconductors.

Going forward, Mitsubishi Electric will continue refiningthe design and specifications of its SiC metal-oxide semiconductor field-effecttransistor (SiC MOSFET) to further lower the resistance of SiC power semiconductordevices. This research achievement was initially announced at The InternationalElectron Devices Meeting (IEDM2017) in San Francisco, California onDecember 4 (PST).

The impact that charges and atomic vibration have onelectron scattering under the SiC interface was revealed to be dominant inMitsubishi Electric’s analyses of fabricated devices. Electron scatteringfocusing on atomic vibration was measured using technology from the Universityof Tokyo. Although it has been recognized that electron scatting under the SiCinterface is limited by three factors, namely, the roughness of the SiCinterface, the charges under the SiC interface and the atomic vibration (seeFig. 1), the contribution of each factor had been unclear. A planar-typeSiC-MOSFET in which electrons conduct away from the SiC interface to around severalnano meters was fabricated to confirm the impact of the charges. As a result,Mitsubishi Electric and the University of Tokyo achieved an unprecedentedconfirmation that the roughness of the SiC interface has little effect whilecharges under the SiC interface and atomic vibration are dominant factors (seeFig. 2).

Compared with a previous planar-type SiC-MOSFET device,resistance was reduced by two thirds owing to suppression of electronscattering, which was achieved by making the electrons conduct away from thecharges under the SiC interface. The previous planar-type device used forcomparison has the same interface structure as that of the SiC-MOSFETfabricated by Mitsubishi Electric.

For the test, Mitsubishi Electric handled the design,fabrication and analysis of the resistance-limiting factors and the Universityof Tokyo handled the measurement of electron-scattering factors.

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